Wave guide impedance element



Aug. 19, 1952 A. G. FOX

WAVE GUIDE IMPEDANCE ELEMENT Original Filed July 30, 1942 FIG. 2

FIG.

lNl ENTOR By A. 6. FOX

A TTORNEY Patented Aug. 19, 1952 2,607,8 50-' I I WAVE GUIDE lMPEDANGEcELEMENT Q 7 Arthur Gardner, Fox, Red Bank; N. 'J., assignor toBell Telephone Laboratories; Incorporated, New YorlQNpYJ, a-corporation of New York Originalfappliiaation July. 30;,1942, Serial Nor... 452,851. Divided and thiswappli'cation,August. 17;;1-845,;Serial,No;610,956

v Thistinventio'n relates to-guided electromagnetic wave transmission"and-more particularly to impedance :elements:andterminations for wave guides. I

An object of the invention'is. toliqrovide 'simple vseries resonant 'impedancexbranch'es' and simple parallel resonant'finipedance branches for use "in waveguides.

. Anotherobject' of thez inventionis 1 to' provide a refie ction'less .terminat'ionifor a, wave guide;

dielectric filler willserv'e'as fai guideior suitable electromagnetic wavesz' Z cross-"section the sheath may "be circular, recta ular; or of other shape; for all frequencies'fabove a minimum, known.1as the cut-01f frequency, "the" guide? act's likea transmission lineandhas' a'specifitrpropagationr constant: and char-act'eristicimpedance. For any particular'frequencyfthere areiarrinfinite number of cross-sectional'jsizesfland" shapes of guide which will have the" same. characteristic impedance.

Shunt reactive elements are obtained" placingrpfirtial.obstructions across the waveguide. For, dominant transverse electric waves a' shunt freactive' element maybe provided'by a transverse metarpartiti'on having'a slit therein which' extends substantially from, one sidetolth'e other. Iffthe s1itis' perpendicular to the direction 'of polarization ofl'the electric field; the. elementwis primarily 1 capacitive, andljifj parallel with the 'fiel'd'the element is nrimarilylinductive. I r accordance with the present invention an aperture'in atransverserpartition in alwave'gui'de is" proportioned' to providejboth linductiveand capacitive components in the. rightamountst'o resonate at aj particular frequency: Depending upon, the shape of the aperture' the' resonance -thus prod'uced'may be eitherof' the paralleltype, ofle'rin'g aYhighshuntimnedanceiacross' the guide,

orofthe'series typ ofierin'gfa low shuntirnpedance: Forexample; a 'rectangularaperturejmay be=proportioned forparallelresonanceor, if'imade suflicientlrnarrow; tori-series resonance: The resonance may be" sharpened by" providing in- I wardly extendingprojections on oppositesides" of the opening: A- wid'eropening mayfbe used-ifflthe opposed edges' of the aperture are' 'ma-de'thicker,

' or-if- "thetwo halves of thepartition are made to overlap.

" Also-in accordance with the invention a reflectionless terminationfor a wave guiderisf provided liy--employing a" parallel=resonant{element followd by means-within the guide for estab'- lishing a point of"zeropotentia1. 'Ihe-element-is*- accordance with-theinvention. i

tition in"awave guide may' bema'de'to provi'de preferablyso designed' th t its' 'efiective shunt-re sistance is" approximately equal to: the charace teristicimpedance of the guide: The "point of 'zero' potential i's'spaced approx-imate'l'y'a quarter wavelength from theelement and may beestab tition:

This is adivi'sion of United--States-application 0} IQ LZIiiOW 'PateIit lished by means of'a solid transverse meta'llic' raare Thenature'of the'invention will be more-amt understoodfrom the following detailed-description and by reference to the-accompanying'draw- :ings: in which like reference characters refento like-parts-andin-"which I Figs: 1 and2 are perspective views=ofwave guides having therein partitions *with aperttnes whiclrprovide=reactivee1ements;

Fig: 3 shows 'awave guide termination-inaccor-dance with theinventi'on-employing a jiarallel resonant elementin r Fig: -shows animpedanceelement in accordance'with the 'inventionthat may-fbe'adjus'ted eitherparallel" or series resonance; and- Fi'gs; 5" .and- 6 showseries -'resonantelements in .Takingggup' the figuresin' more detaili Fig: 1

is: a perspective -view* of a section of a rnet'alli'c wage guide I in "the form off'arectangular'sheath whichihas been cross-sectioned just ahead 01 17118 transverse metallic partition; comprising an"up'- perportion Tanda lowerportiontwi-th an" aperture '4 therebetweemextendihg from one side of the guideto'theother. "If" the'guide-l is carrying 5 dominantitransverse electric waves theelecj tricfifi'el d"-E-: polarized in-a direction perpendicu- "lar' to the length'of the aperture 4", as indicated bythe' arrow; the partition will providea shunt capacitive reactancjez' The" magnitudeof'this reactance" depends" upon-the width of the-aperdecreases-as thetwidthris decreased; 7

Fig; 2 is similar toFig: "1 except that theaperguidel and'has'itslengthparallel tothe direction ofthe electric field" E2 A partitionoff'this" type providesra shuntinductive react'ance; the magnitude' of which also decreases asthe width of the aperture"*li-tdecreases. I .BY'pr rie i m t b r' fap tn a rbothinductive and capacitive comp nents-"in 'tlie right amounts toweson atepat a; particulan'freen i imw ria ara le fi anq or'a seriesresonance; For example, jFfg. *3 shb'ws a parallel-resonant element, that is, one provide ing a high'shunt impedance, in a rectangular height V or the width W has been chosen, the

other dimension is thereby determined. The line I3 gives the locus of the upper right-hand corner I4 of all possible rectangular apertures that I will provide parallel resonance in the wave guide I. 7

Associated with each height V of the aperture l2 in the parallel-resonant element shown in,

Fig. 3 there will be a resistance which is eflec-H tively shunted across the guide I. The value of this resistance decreases as the dimension V 'decreases and its range may extend from a small fractionof the characteristic impedance of the guide I toinfinity. It is possible, therefore, to design a particular resonant aperture which will have a shunt resistance equal to the characteristic impedance of the guide; Such an element placed inthe guide and followed by a solid metallicpartition such as I5 placed one-quarter of a wavelength behind the element II will serve as a reflectionless termination for the guide I. A termination of thistype uses no conventional resistance elements. 7 The power is dissipated by high circulating currentsin the metal partition I] t which has highthermal conductivity and is in metallic contact with the :walls of the guide I and therefore is capable of dissipating a large amount of'power .The element I l whenused in a termination of the type describeduis preferably made of a metal having comparatively low electrical conductivity such, for example, as iron, since it. is thereby possible to make the aperture larger. V

' Fig 4 shows a circular guide I having therein an impedance element which may be adjusted for I either parallel resonance or series resonance.

;-'I'he partition IB- has a rectangular aperture into which project a pair of threaded studs I'I having-their axes along a diameter of the guide I and parallel to the electric field E. The two in-- ternally threaded sleeves I8, each with a circular metal plate I9 fastened to one end, may be screwed onto the studs [1. The separation between the plates I9 may thusbe adjustedas desired. For series resonance only a small separation is required. For parallel-resonance the spacing will begreater and in this case the plates I9 maynot be requiredr -An advantage of using an aperture with one or moreinwardlyextending: projections, as shown .in Fig. 4, is that sharper resonances may be obtained;

. Fig. 5: shows an element more particularly adaptedfor series resonance, providing a low shunt impedance. The partition [6, has a sym-, metrical aperture having its length perpendicular to the electric field E and its width constricted toward the center by means of the inwardly extending projections 2| and 22, to which are attached, on opposite sides of the partition I6, two overlapping metal flaps 23 and 24. These element. a

' Fig. 6 shows a modification of the seriesresonant element of Fig. 5 in which the flaps 23 and Mare replaced by two opposing metallic netic waves therein, a'partition transversely dis- '4 plates 25 and 26 which are perpendicular to the partition I6 and attached to the ends of the projections 2| and 22.

Since a metallic obstruction in a wave guide usually produces a point of low potential and vhigh .curernt, it is preferable thatthe partitions be secured to the walls of the guide'by soldering, welding or in some other appropriate manner such that a good electrical contact is obtained, It should also be noted that thinner partitions than those shown in the drawings, will, under some circumstances, produce more satisfactory results. The partitions have been shown thicker in the drawings only in the interest of clarity.

Certain subject matter disclosed herein is claimed in application Serial No. 266,179 filed aperture .inthe direction of polarization ofthe electric field of said waves and the width of said aperture in a direction perpendicular thereto being proportioned with respect to each other to provide at said point a shunt impedance branch 1 which is resonant at the frequency of said Waves.

2. The combination in accordance with claim 1 in which said partition is comparatively thin.

3. The combination in accordance with claim 1 in which said aperture is symmetrically positioned in said partition. 1 w

4. The combination in accordance with claim 1- in which said. guide is rectangular in cross-sec tion. Y f

5. In combination a conductivelyj sheathed wave guide, means for establishing electromagnetic waves therein, a partition transversely ,disposed at a point in said guide and'a rectangular aperture in said partition, the height of said aperture in the direction of polarization of the electric field of said waves and the width ofsaid aperture in a direction, perpendicular thereto being proportioned with respect to each other to provide at said point .av shunt impedance branch which is parallel-resonant at. the frequency of said waves.

'6. In combination, a conductively sheathed wave guide, means forestablishing electromagposed .at apointin said, guide, and a rectangular aperture. in said partition, the height, of,.said aperture. in the direction of polarization of the electric field of said waves and the width ofsaid aperture in a direction,-perpendicular thereto being proportioned with respect to each other to provide at said point a shunt impedance branch which is parallel-resonant at the frequency-of said waves and the resistance of said branch being approximately equal-to-the characteristi impedance of said guide.

7. vThe combination in accordance with claim 6 and means within said guide for establishing a point of zero potentiaLsaidmeans being spaced from said partition approximately a quarter of a wavelength at said frequency.

8. The combination in accordance with claim 7 in which said partition is made of a metal hav-' ing comparatively low electrical conductivity.

9. The combination in accordance with claim 8 in which said metal is iron.

10. The combination in accordance with claim 5 and a solid metallic transverse partition within said guide spaced from said apertured partition approximately a quarter wavelength at said frequency, the efiective shunt resistance'associated with said apertured partition being approximately equal to the characteristic impedance of said guide.

11. In combination, a conductively sheathed wave guide, means for establishing therein electromagnetic waves, and an apertured partition transversely disposed in said guide, said partition being parallel-resonant at the frequency of said waves and the effective shunt resistance associated with said partition being approximately equal to the characteristic impedance of said guide.

12. The combination in accordance with claim 11 and means for establishing a point of zero potential within said guide approximately a quarter wavelength from said partition.

13. In combination, a metallic pipe-shaped guide having a rectangular cross-section for propagating electromagnetic Waves dielectrically, exciting means for establishing within said guide electromagnetic waves, and a partition substantially perpendicular to the direction of propagation of said waves, said partition being provided with a rectangular shaped slot which is tuned to be resonant to the frequency of said waves.

14. In combination, a hollow-pipe type wave guide for transmitting electromagnetic waves dielectrically, exciting means for establishing electromagnetic Waves in said guide, a metallic wall member associated with said guide and positioned transverse thereto relative to the direction of wave propagation through said guide and comprising an opening tuned to the frequency of the exciting means thereby effecting a concentration of the potential incident to the waves, and means for controlling the effective dimensions of said opening for controlling the frequency at which said opening is resonant.

15. In combination, a :wave guide comprising essentially a pipe-like member, means connected to said member for establishing electromagnetic waves within said member, a wall member substantially perpendicular to the longitudinal axis of said first member and having therein an aperture which is tuned to the frequency of exciting electromagnetic waves to effect a concentration of one component of the electromagnetic field for producing a concentrated region of the field intensity, and means for controlling the effective dimensions of said aperture for controlling the frequency at which said aperture is resonant.

16. In combination, a dielectric wave guide of the hollow-pipe type, exciting means for establishing electromagnetic waves within said guide, a metallic wall positioned in said guide and lying in a plane substantially transverse to the direction of wave propagation through said guide and provided with an aperture having an appreciable dimension perpendicular to the electric component of the field incident to the propagation of said waves through said guide and tuned to the frequency of said exciting means, and means for controlling the effective dimensions of said aperture and for controlling the frequency at which said aperture is resonant.

17. In combination, a dielectric wave guide of the hollow-pipe type, exciting means for establishing electromagnetic waves within said guide, a metallic wall positioned in said guide and lying in a plane substantially transverse to the direction of wave propagation through said guide and provided with an aperture having an appreciable dimension perpendicular to the electric component of the field incident to the propagation of said waves through said guide and tuned to the frequency of said exciting means, and mechanical means for controlling the effective dimensions of said aperture and for controlling the frequency at which said aperture is resonant.

18. In combination, a dielectric wave guide of the hollow-pipe type, exciting means for establishing electromagnetic waves within said guide, a metallic wall positioned in said guide and lying in a plane substantially transverse to the direction of wave propagation through said guide and provided with an aperture having an appreciable dimension perpendicular to the electric component of the field incident to the propagation of said waves through said guide and tuned to the frequency of said exciting means, and means for controlling the eifective configuration of said aperture and for controlling the natural resonance frequency thereof.

19. In combination, a metallic pipe-shaped guide having a rectangular cross section for propagating electromagnetic waves dielectrically, exciting means for establishing within said pipelike member electromagnetic waves, and a radiative wall substantially perpendicular to the direction of propagation of said waves and being provided with a rectangular shaped slot which is tuned to be resonant to the frequency of said exciting means.

ARTHUR GARDNER FOX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,200,023 Dallenbach May 7, 1940 2,206,923 Southworth July 9, 1940 2,238,770 Blumlein Apr. 15, 1941 2,241,119 Dallenbach May 6, 1941 2,253,589 Southworth Aug. 26, 1941 2,281,274 Dallenbach Apr. 28, 1942 2,323,201 Carter June 29, 1943 2,368,031 Llewellyn Jan. 23,1945 2,375,223 Hansen May 8, 1945 2,402,184 Samuel June 18, 1946 

